System design interviews are the highest-signal round for SDE-2+ roles at top companies. They test whether you can think at scale, make tradeoffs, and communicate technical decisions clearly. Here's a step-by-step preparation framework.
The 5-Step Framework
Follow this framework in every system design interview:
1. Requirements (3-5 min) — Clarify functional and non-functional requirements. Ask about scale, latency, consistency requirements.
2. Estimation (2-3 min) — Back-of-envelope math. How many users? QPS? Storage? Bandwidth?
3. High-Level Design (10 min) — Draw the major components: clients, load balancers, application servers, databases, caches, message queues.
4. Deep Dive (15-20 min) — The interviewer picks 1-2 areas to go deep. This is where you differentiate yourself.
5. Tradeoffs & Extensions (5 min) — Discuss what you'd change for 10x scale, what you'd monitor, how you'd handle failures.
Top 15 System Design Questions
Most-asked across Google, Amazon, Flipkart, and startups:
1. Design URL Shortener (like bit.ly)
2. Design a Chat Application (like WhatsApp)
3. Design a News Feed (like Facebook/Instagram)
4. Design a Rate Limiter
5. Design a Notification System
6. Design Twitter/X
7. Design YouTube (video streaming at scale)
8. Design an E-commerce System (like Flipkart)
9. Design a Payment System (like Razorpay)
10. Design a Search Autocomplete
11. Design a Ride-Sharing Service (like Uber/Ola)
12. Design a File Storage System (like Google Drive)
13. Design a Distributed Cache
14. Design a Job Scheduler
15. Design a Metrics/Monitoring System
Key Concepts You Must Know
• Load Balancing — Round-robin, consistent hashing, L4 vs L7
• Caching — Redis/Memcached, cache-aside vs write-through, eviction policies
• Database — SQL vs NoSQL, sharding strategies, replication
• Message Queues — Kafka, RabbitMQ, async processing
• CDN — How CDNs work, cache invalidation
• Consistency Models — Strong, eventual, causal consistency
• CAP Theorem — You can't have all three: choose two
• API Design — REST vs GraphQL, rate limiting, pagination
• Microservices — Service discovery, circuit breakers, saga pattern
India-Specific Tips
Indian tech interviews often include constraints that US interviews don't:
• COD (Cash on Delivery) handling in e-commerce systems
• UPI/IMPS payment integration in payment systems
• Multi-language/script support (Hindi, Tamil, Bengali)
• Low-bandwidth optimization for tier-2/3 city users
• India's data localization requirements (RBI mandates for financial data)
• Spike handling for events like Flipkart Big Billion Days or IPL streaming
Mentioning these shows domain awareness and impresses Indian interviewers.
Preparation Timeline (4 Weeks)
Week 1: Learn the fundamentals — caching, databases, load balancing, message queues
Week 2: Practice 3 classic problems (URL shortener, chat app, news feed)
Week 3: Practice 3 harder problems (payment system, search, ride-sharing)
Week 4: Mock interviews — practice explaining your design out loud
Resources: System Design Primer (GitHub), Designing Data-Intensive Applications (book), HireStepX's AI system design interviews
Frequently asked questions
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